Add an attribute for `extra words`

## Short Description

Adding a new integer attribute `extra_words` to each matched license.

## Select Category

- [x] Enhancement
- [ ] Add License/Copyright
- [ ] Scan Feature
- [ ] Packaging
- [ ] Documentation
- [ ] Expand Support
- [ ] Other

## **Describe the Update**

There are two cases when calculating score,

1. If `score` == `match_coverage` * `rule_Relevance`, then there are no
extra words in that license match.
2. If `score` != `match_coverage` * `rule_Relevance`,
then there are extra words in that match. (all the words in the rule are present, but there are more words)

In the second case, the score is decreased based on how much extra words is there, and presently
this isn't returned.

## **How This Feature will help you/your organization**
Will help in `scancode-results-analyzer`

## **Can you help with this Feature**
Yes.